Search for fundamental physics with H.E.S.S. & CTA Christian Farnier Oskar Klein Centre – Stockholm University WIN2013 Natal, Brazil September, 16th - 21th
OUTLINE VHE astronomy Imaging Atmospheric Cherenkov Telescopes Few results on the search for fundamental physics Conclusion Christian Farnier WIN2013 – Natal, Brazil 2
γ -ray astronomy : probing the non-thermal Universe Galactic sources SNR SNR PWN Pulsar Binary DM ? Galaxy cluster ? Axion ? GRB AGN Starburst galaxy Extragalactic sources Christian Farnier WIN2013 – Natal, Brazil 3
Detecting γ -rays VHE, HE Convention HE : High Energy (E ≥ 100 MeV) VHE : Very High Energy (E ≥ 100 GeV) γ -rays are not deflected by B →study of sources and production mecanisms Atmosphere is opaque to γ -rays Satellite exp. for HE IACTs for VHE (very low fluxes 10 -(11-12) ph cm -2 s -1 ) Christian Farnier WIN2013 – Natal, Brazil 4
Imaging Atmospheric Cherenkov Telescope (IACT) principle Backgrounds: ● the night sky (stars, Moon, …) : duty cycle ~1000h/y ● Charged cosmic rays (p,e,...) rate x10 5 higher than the brightest TeV γ -ray source. Christian Farnier WIN2013 – Natal, Brazil 5 Credits : W. Hofmann
IACT principle (cntd) Cherenkov photons production. Shower development Ultra fast (~10ns) recorded in the focal acquisition camera. plane. Image based event selection / background Image parameters reco. rejection. (direction, energy) Christian Farnier WIN2013 – Natal, Brazil 6
IACTs - Stereoscopic system In the current experiments, up to 5 IACTs are put together, allowing to observe the same shower from several point of view. Advantages : ● Improved bckg rejection (muons) ● Incoming direction degeneracy dispelled ● Improved angular resolution ● Improved energy resolution + new shower reconstruction algorithms developped based on intrinsic 3D shower properties. Christian Farnier WIN2013 – Natal, Brazil 7
Census of IACT experiments VERITAS MAGIC FACT HESS CANGAROO (ended) Christian Farnier WIN2013 – Natal, Brazil 8
The most advanced : H.E.S.S. 2 ∅: 13m ∅: 28m Phase 1 : 4x Phase 2 : + 1 Camera :1 ton, 960 PMTs Camera :2 ton, >2000 PMTs Begining of operation : 2004 Begining of operation : 09/2012 Christian Farnier WIN2013 – Natal, Brazil 9
H.E.S.S. astrophysical results H.E.S.S. galactic sources + 19 extragalactic sources Christian Farnier WIN2013 – Natal, Brazil 10
CTA - Cherenkov Telescope Array 27 countries Currently in the preparatory phase > 1000 scientists Construction phase will start in 2014 2 arrays >1000 sources expected 3 types of telescopes ~ 1000h obs/y Christian Farnier WIN2013 – Natal, Brazil 11
CTA : the ''perfect'' stereoscopic system The most advanced stereoscopic systems have only 5 (4) telescopes H.E.S.S. (VERITAS). CTA will have dozens (to cover an area O(km^2)), most probably of 3 (or 4) different sizes : Large : 24m Medium : 12m Small : 6-8m Which will allow cover broader energy range and improve the performances : CTA consortium 2012 Angular & energy resolutions, Background rejection, Sensitivity, …. Christian Farnier WIN2013 – Natal, Brazil 12
CTA observatory First open observatory in the VHE domain Large number of users from different fields of science Christian Farnier WIN2013 – Natal, Brazil 13
Some searches for fundamental physics : 1.Dark matter 2.Axion-like particles 3.Lorentz Invariance violation 4.Primordial black holes Christian Farnier WIN2013 – Natal, Brazil 14
1. Dark matter in the Universe – really ? Coma galaxy cluster Fritz Zwicky, 1933: ”If this over-density is confirmed we would arrive at the astonishing conclusion that dark matter is present with a much greater density than luminous matter.” Bergstrom, Rep. Prog. Phys. 2000 Planck, 2013 Clowe et al., 2006 YES ! At all scale. Christian Farnier WIN2013 – Natal, Brazil 15
γ -ray flux from WIMP annihilations Astrophysic factor : Particle physic factor : determine the nb of determine the nb of γ -ray annihilations produced per annihilation → intensity of gamma-rays → spectral shape Uncertainties : Uncertainties : density profile, diffusion, cross section, mass, absorption,... branching ratios,... Christian Farnier WIN2013 – Natal, Brazil 16
DM targets for indirect γ -ray searches Pros: increasing number of objects, bckg free Dwarf Cons: amount of DM limited galaxies Galactic Pros: large integration region, DM profile well estimated Halo Cons: bckg Pros: high DM density Galactic Cons: large uncertainties, several std γ -ray accelerators Centre k l a t s i h t n i Pros: number of sources, large amount of DM d Galaxy e r e Cons: distance, bckg Clusters v o c t o N Pros: large integration region Extragalactic Cons: low DM density, bckg Christian Farnier WIN2013 – Natal, Brazil 18
Dwarf spheroidal galaxies Dwarf galaxies probed in gamma-rays as in 2012 Veritas Fermi H.E.S.S. MAGIC Christian Farnier WIN2013 – Natal, Brazil 19
Why dwarf galaxies ? DM dominated (M/L ~ 10 – 100) Nearby (~100 kpc) Low background (ordinary matter content very low) Stellar velocities can be used to estimate DM density (error can be propagate to particle constraints) Christian Farnier WIN2013 – Natal, Brazil 20
H.E.S.S. results Signal search : ON (target region) - OFFs (CR bckg determination) Flux upper-limit determination : Φ UL = f(N obs , A eff , T obs , DM model(m DM )) Correspondance into annihilation cross-section : < σ v> UL = f( Φ UL , DM model(m DM ), J) Sculptor dSph Carina dSph Sagittarius dSph H.E.S.S. Coll, 2007-2011 Christian Farnier WIN2013 – Natal, Brazil 21
Prospects H.E.S.S. II and CTA will be more sensitive thanks to lower energy threshold Exemple : CTA – 100h Classical vs ultra-faint dSph CTA consortium 2012 Still above the thermal relic density But stacking will also improve our results, see Fermi-LAT results Similar analysis currently ongoing in H.E.S.S. Fermi collab, 2011 Christian Farnier WIN2013 – Natal, Brazil 22
The Galactic halo with H.E.S.S. Observation regions DM density vs distance from the GC γ -like events spectrum signal, bckg and excluded Corresponding DM densities Observation results : regions definition no significant excess T obs = 112h Most constraining results on the DM searches for large massive particles (m WIMP ~ 400 GeV). But still above viable DM models. Better sensitivity is required. H.E.S.S. collaboration, 2011 Christian Farnier WIN2013 – Natal, Brazil 23
CTA prospects 5° CTA consortium 2012 ● Increased FOV → larger difference of DM content between ON and OFF regions ● Simulations indicates that the Galactic halo is the most promising location for CTA indirect DM search. ● In only 50h of observations, CTA will probe SUSY models compatible with WMAP results. Christian Farnier WIN2013 – Natal, Brazil 24
Line search with H.E.S.S. Integration region similar to halo analysis Data set : 4-tel. events ( ∆ E/E), 2004-2007 [112h] (E th ) No OFF subtraction Bckg (« g-like » CRs) spectrum fitted Profile likelihood search of a line-like signal H.E.S.S. Coll. 2013 on top of background H.E.S.S. II prospects H.E.S.S. Coll. 2013 HESS coll. 2013 Christian Farnier WIN2013 – Natal, Brazil 26 Bergström, Bertone, Conrad, CF , Weniger., 2012
And next with CTA CTA expectations Confirmation of Weniger (2012) line >5 σ in 5h [syst. uncertainties] 1 vs 2 lines distinction reachable with additional time and refined analysis Bergström, Bertone, Conrad, CF , Weniger., 2012 Christian Farnier WIN2013 – Natal, Brazil 27
Not only gamma-rays ! Search for electrons (+positrons) Extragalactic regions (low gamma-ray content) Large collection area and exposure time Analysis and results Electron identification from simulations + Random Forest Power-law + break @ 1 TeV Disproved ATIC peak and its DM interpretation H.E.S.S. coll., PRL 2008 & A&A 2009 Christian Farnier WIN2013 – Natal, Brazil 28
2. Axion-like particles Same phenomenology as true axion (Peccei & Quinn, 76) but m a and g γ a unrelated γ /ALP oscillations in external magnetic field... ...possible modification of opacity of the Universe to TeV gamma-rays. Important for very distant sources detected in gamma-ray. Conversions γ /ALP introduce irregularities in gamma-ray spectrum amplitude driven by g γ a location driven by m a Wouters & Brun, PRD, 2012 Christian Farnier WIN2013 – Natal, Brazil 29
Axion-like particles H.E.S.S. results Search for irregularities in PKS2155 flare spectrum Look for anomalous deviations in triplet of successive bins Statistical analysis on MC L ↔ size of conversion domain s ↔ coherence length H.E.S.S. collab. submitted Christian Farnier WIN2013 – Natal, Brazil 30
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